The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art.
Visible light communication (VLC) is a communication technology, which utilizes light in the visible light Line Of Sight (LOS) channel environment with a light emitting diode (LED) and a photo detector (PD) to transmit and receive data.
Visible light communication uses blinking light for communications to require no permission for the use of a frequency spectrum, and it is harmless to the human body. In addition, visible light communication performs communications within the coverage of light, which can advantageously provide a specified range of communication. Visible light communication technologies conform to IEEE 802.15.7 standards, and active researches are now carried out in this field for improving data transmission/reception speed.
However, the visible light communication requires a photodetector for data reception, which increases the cost of constructing a communication system. As a solution, optical camera communication (OCC) has been proposed.
Optical camera communication is an applied technology of visible light communication, which uses a camera built in a smart device such as a smartphone or a digital camera as a photodetector.
The use of a camera, particularly an image sensor as a light detector in optical camera communication is advantageous in that a communication system can be constructed by utilizing the existing LED light source infrastructure, requiring neither modification nor additional cost. In the field of optical camera communication, standardization work is in progress on IEEE 802.15.7a, and researches are being actively carried out on utilization strategies with LED signboards and digital signage, etc.
FIG. 1 is a schematic diagram of an optical camera communication system.
Referring to FIG. 1, an optical camera communication system 100 may include an LED light source 110 and an optical camera 130.
The LED light source 110 may transmit the transmit data by blinking light (that is, turning on/off the LED) based on binary information of transmit data. In addition, the LED light source 110 may simultaneously perform the lighting function and the communication function by blinking the light at a frequency of 100 Hz or more so that a person cannot recognize it.
The optical camera 130 may receive the transmit data from the LED light source 110 by using an image sensor (not shown). The optical camera 130 may receive the transmit data by subjecting the received optical signal to signal processing by spatially separating the received optical signal into each pixel of the image sensor.
Meanwhile, the speed of capturing moving images by the optical camera 130 is generally 30 fps (frame per second), but in practice it is variable irregularly. Therefore, in optical camera communication, the transmit data transmitted at a constant speed is sampled irregularly via the optical camera 130, resulting in the loss of the transmit data during data transmission and reception.